The overall objective is to define the location and ultrastructure of sensory receptors in normal and abnormal teeth and periodontium. We will use autoradiographic techniques to map gasserian and mesencephalic nerve endings in dental tissue of rats and cats and to map sympathetic nerves in rats. Electron microscopy will be used to define receptor structure, nerve odontoblast associations, and axon spectra for intra dental endings in rat molars and cat teeth, and to compare free and encapsulated periodontal endings. The ultrastructural studies will use special stains to enhance membrane ultrastructure. Finally, we will study receptor structure in reinnervated rat molars, and beneath cavity preparations in rat molars. These studies will lead to improved understanding of dental sensory mechanism and, since teeth are primarily painful, to the understanding of pain receptor structure.